Well, this is a bit counterintuitive. Spotted by asobinet, Canon has patented a mechanism for a zoom lens mechanism that actually gets shorter as you increase the focal length. Yes, that’s right, the exact opposite to how zoom lenses normally work.
The patent was published on November 18th to provide zoom lenses with large apertures and small size with high optical performance. A number of lens examples are included in the patent, including a couple with ranges of approximately 28-70mm and 28-60mm with f/2.8 and f/4 maximum apertures respectively.
The patent describes the problem that it solves:
INDUSTRIAL APPLICABILITY: A zoom lens and an image pickup device having the same.
PROBLEM TO BE SOLVED: To provide a zoom lens having a large aperture ratio and a small size but having high optical performance, and an image pickup apparatus having the same.
In recent years, with the increasing functionality of image pickup devices, there is a demand for a compact and lightweight zoom lens having a large aperture ratio. As a zoom lens that satisfies this requirement, a negative lead type zoom lens in which a lens group having a negative refractive power is arranged on the most object side is known.
An object of the present invention is to provide a zoom lens having a large aperture ratio and a small size but having high optical performance, and an image pickup apparatus having the same.
It then goes on to describe the aforementioned 28-70mm f/2.8 and 28-60mm f/4 zoom lens specifications.
Focal length: 28.84-67.90
F value: 2.91
Half angle of view: 32.65-17.67
Image height: 21.64
Overall length: 149.46-115.94
Back focus: 13.48-27.78
Focal length: 28.84-60.00
F value: 4.12
Half angle of view: 32.68-19.83
Image height: 18.50-21.64
Overall length: 141.33-104.61
Back focus: 19.70-35.51
Physically, both lenses appear to be approximately the same size at the short end but shrink down as you zoom in, which sounds kind of weird, but also cool. Whether or not this technology will be implemented in the real world and how practical it would be remains to be seen. If such lenses do come to fruition, though, I wonder if we’ll start to see the focal length lock at the long end of the range instead of the short end in order to keep them more compact for storing in our camera bags.
Unfortunately, no link was posted to the original patent, but you can find out more about it here.